The correct structure of 4-bromo-3-methyl but-1-ene is

The IUPAC name given is 4-bromo-3-methyl but-1-ene which suggests that longest carbon chain is of 4 carbons, double bond at 1 position and Bromo group at 4th position. Thus, the correct option is (b) 2 3 2 CH CH CH(CH ) CH Br